This invention relates to an ink cartridge for an ink jet printing apparatus, such as an inkjet printer.
In many ink jet printers, the ink reservoir is contained in a removable ink cartridge, which may also contain the ink delivery components. Such ink cartridges typically consist of an ink reservoir, some form of pressure regulator, an ejector chip, a filter, and ink passages from the ink reservoir to the chip. With thermal inkjet technology, the chip heats the ink and jets it out through a nozzle plate. The pressure regulator keeps the ink entering the chip at a slight negative pressure.
In existing art, the ink reservoirs are often formed by walls or partitions molded into the cartridge body, and pressure regulation is accomplished by inserting a piece of foam into each of the ink reservoirs. The capillary action of the foam creates backpressure for the chip, and the pore size of the foam when compressed determines the ink backpressure.
One aspect of the cartridge design to consider is how it is filled. The standard method to fill a cartridge is to pump the ink through a needle that passes through the lid and is inserted into the foam. The needle extends down through the foam and stops just above the filter. The needle height in this process is critical as it affects the ink saturation around the filter area. It is often difficult to get good saturation when this method is used. If the needle is too close to the filter, some ink is forced through the filter and into the ink channel during ink fill. This wets part of the ink channel and allows air bubbles to remain in the ink channels during prime, preventing a complete prime. If the needle is too high off the filter the ink travels to the top of the foam and begins pooling before the foam around the filter is complete saturated. The pooling ink can contaminate the lid weld surfaces preventing a good weld and also can cause cross contamination between colors.